Curled micro-cantilevers using benzocyclobutene polymer and Mo for wafer level probing

We verified by experiments that only the compressive stressed Mo layer was enough to deflect after release because self-stress gradient originated from strain difference along thickness. This circumstance normally occurred in the sputtered thick films as the crystallography/microstructure difference along the thickness. The deflection height and contact-force at the fully compressed state were found as 128 μm and 231 μN, respectively, in conditions of 2.48 μm thickness and 500 μm length of Mo single layer. These figures are enough to apply to the wafer level testing and interconnects. In addition, composite probe, consisting of Mo metal film and BCB polymer, was analyzed numerically and fabricated for the first time in order to increase the contact-force/stiffness, and for electrical isolation in high frequency devices testing. However, the resultant composite probe showed weak structural properties due to the low stress of BCB and poor adhesion between Mo and BCB. The stress control of BCB layer and process modification for good adhesion were found as solutions for applicable composite cantilever-type probe fabrication.